1. Field of the Invention
This invention relates to a method to manufacture a composite reinforced utility conductor for use in aerial, underground and underwater transmission, distribution and service for electrical and communication utilities, and more particularly, to a reinforced utility cable and a method and an apparatus for producing such a cable by molding and hardening a polymer embedded with continuous filaments or tape in a thermally controlled protrusion die.
2. The Prior Art
The metal used for electrical conductors is selected for the desired electrical properties but the metal is structurally weak in terms of the strength needed for suspending the conductor as an electric transmission line and also for withstanding the forces imposed by wind and ice. To overcome this problem, the electric transmission line is made by wrapping several electrical conductors around a strong steel core. The steel reinforced conductors attached to poles or towers are exposed to the elements using the atmosphere for insulation between transmission lines.
Pultrusion is a well known method for processing material to form a finished product having a desired cross sectional dimension and physical properties imparted by pulling the product along a converging surface of an elongated die. The pultrusion method is used according to the present invention for a cost effective process to apply insulation material and if desired a semi-conducting coating to aluminum or a copper electrical conductor or a light guide cable and controlling sensible heat occurring during the catalyzing action of the polymer in the die. Embedded in the insulation material during passage through the protrusion die are stands of filament and additionally in a light die cable, one or more strands of tape impart the desired strength.
It is an object of the present invention to provide a reinforced utility cable enveloped in a mass of catalyzing polymer which is molded and hardened in an elongated die wherein the temperature is incrementally varied along the length of the die.
It is a further object of the present invention to provide a manufacturing process and apparatus for a reinforced utility cable including passing a molded and hardened fiber reinforced utility cable through a looper to work the cable at ambient temperature by repeated reverse bending prior to coiling.
It is another object of the present invention to provide a reinforcing utility cable and a method and apparatus for producing the same characterized by one or more strands of fiber of tape in a catalyzed polymer encased within a catalyzed polymer containing carbon fiber to form an electromagnetic shield, which is in turn encased with a catalyzed polymer.
In accordance with the present invention there is provided a method apparatus for manufacturing a composite reinforced utility cable by selecting an utility conductor with an applied grease like film that may contain micronized carbon and then compressing reinforcing filaments which have been coated with epoxy, polyurethane, or similar polymers followed by passing the newly formed bundle through a heated die. The selected polymer is preferably dicyclopentadiene and a catalyst may be introduced into the die along with the bundle consisting of the utility conductor and reinforcing filaments, and controlling the die temperature to control the exothermic catalytic reaction, thus producing a composite reinforced, insulated conductor of sufficient mechanical strength to withstand aerial installation, and with sufficient dielectric strength to allow for close spacing of the electrical conductors to overcome induction problems when transmission lines constructed parallel metallic structures such a natural gas lines in a utility corridor, and overcoming problems of short circuit arcing to trees in narrow rights-of-way.
Additionally, a high voltage underground or coaxial cable can be made by passing the composite reinforced conductor previously described through a second process by compressing carbon fibers and conductors which been previously dipped in epoxy or polyurethane, or similar material, around the composite reinforced conductor or introducing dicyclopentadiene and a catalysis to the composite reinforced conductor when the newly formed bundle is again forced through a thermally controlled die. The carbon fiber containing conductors functions as an electromagnetic shield as in axial cables and provides a test point for monitoring current leakage to forecast failure in high voltage cable in subterranean placement sites. A third pass through a thermally controlled die is used to apply an outer layer of only a catalyzed polymer to cable used in coaxial and high voltage underground applications.
More particularly according to the present invention there is provided an apparatus for forming a sheathed utility cable including the combination of an applicator for applying a mass of a catalyzed polymer to a utility conductor and plurality of strands of reinforcing filaments, a protrusion die having an elongated continuous flow space for passage of bundle consisting of a caterized polymer, utility conductor and reinforcement filaments discharged from an applicator, a sleeve surrounding said protrusion die for forming an annular chamber there between, a plurality of closure members at spaced apart locations along an annular chamber for forming discrete chambers for passage of a fluid medium, inlet and outlet conduits connecting to each of the discrete chambers for passage of a fluid medium, a controller for a fluid medium passing to each of the discrete chambers for maintaining a predetermined thermal gradient along the protrusion die, and a driven puller for continuously advancing a bundle from the die.
The present invention also provides a method to reinforce a conductor of a utility transmission line, the method including the steps of selecting a transmission line for a desired utility, selecting a plurality of strands of filaments to mechanically reinforce the utility transmission line, selecting a polymer treated with a catalyst to encase the strands of filament and the transmission line, pulling the strands of filament and the transmission line encased in the treated polymer through an elongated protrusion die to form an electrically insulated and reinforced utility cable, maintaining an elevated temperature gradient along the die to control the physical property of the polymer as the polymer catalyze, bending the polymer in reversed directions after emerging from the protrusion die during completion of the catalyzing and during cooling to ambient temperature to avoid the occurrence of a permanent set in the catalyzed polymer, and coiling the newly formed electrically insulated and reinforced utility cable.
The present invention includes the combination of a reinforced utility cable including the combination of strands of a utility conductor collected in a bundle formation, a coating of grease on the strands in the bundle of strands and a coating of lubricant on the outer periphery of the bundle of strands, at least one reinforcing ribbon arranged substantially about the grease coated bundle of strands, and a sheathing of catalyzed polymer enveloping the reinforcing strand of utility conductors.